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Does Childhood Obesity Mean a Shorter Life? Not Necessarily

A study of ﻿Pima and Tohono O’odham Indians, reported today in The New England Journal of Medicine, found that the subjects who were fattest as children were more than twice as likely as those who were thinnest to die before age 55 from "endogenous causes" (disease or self-injury). The lead author says this finding "suggests that obesity in children, even prepubescent children, may have very serious long-term health effects through midlife—that there is something serious being set in motion by obesity at early ages." Or, as the New York Times headline puts it, "Child Obesity Risks Death at Early Age."

That may be true, but the details of the study complicate the casual equation of fatness with poor health. While children who were in the fourth (highest) quartile for body mass index were 2.3 times as likely to die early as children in the first (lowest) quartile, the death rates in the second and third quartiles were statistically indistinguishable from the death rate in the first quartile. Those results are consistent with other research indicating that the health risks associated with high BMI are concentrated among the very obese, while the medical profile of people who are merely "overweight" is either not much different or somewhat better than that of people in the weight range that the government considers ideal.

Even among the subjects in the highest quartile, the risk factor for premature death shrank from 2.3 to 1.4 when the researchers controlled for baseline glucose level, cholesterol level, and blood pressure. Furthermore, while some of the deaths were due to causes, such as cancer and diabetes, that may be related to obesity (or the diet associated with it), others are less plausibly blamed on overeating. Sixty-eight of the 166 deaths were caused by alcohol abuse or drug overdose, for instance, while another 33 were due to unspecified "other causes." In short, it's not clear to what extent the association between obesity and premature death was due to excess weight per se, which is a general problem with research on the health implications of BMI.